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BABY BOOM target genes provide diverse entry points into cell proliferation and cell growth pathways

Passarinho, Paul, Ketelaar, Tijs, Xing, Meiqing, van Arkel, Jeroen, Maliepaard, Chris, Hendriks, Mieke Weemen, Joosen, Ronny, Lammers, Michiel, Herdies, Lydia, den Boer, Bart, van der Geest, Lonneke, Boutilier, Kim
Plant molecular biology 2008 v.68 no.3 pp. 225-237
Arabidopsis, Brassica napus, actin, biosynthesis, callus formation, cell growth, cell proliferation, cell walls, genes, microarray technology, microfilaments, phenotype, protein metabolism, seedlings, somatic embryogenesis, transcription (genetics), transcription factors
Ectopic expression of the Brassica napus BABY BOOM (BBM) AP2/ERF transcription factor is sufficient to induce spontaneous cell proliferation leading primarily to somatic embryogenesis, but also to organogenesis and callus formation. We used DNA microarray analysis in combination with a post-translationally regulated BBM:GR protein and cycloheximide to identify target genes that are directly activated by BBM expression in Arabidopsis seedlings. We show that BBM activated the expression of a largely uncharacterized set of genes encoding proteins with potential roles in transcription, cellular signaling, cell wall biosynthesis and targeted protein turnover. A number of the target genes have been shown to be expressed in meristems or to be involved in cell wall modifications associated with dividing/growing cells. One of the BBM target genes encodes an ADF/cofilin protein, ACTIN DEPOLYMERIZING FACTOR9 (ADF9). The consequences of BBM:GR activation on the actin cytoskeleton were followed using the GFP:FIMBRIN ACTIN BINDING DOMAIN2 (GFP:FABD) actin marker. Dexamethasone-mediated BBM:GR activation induced dramatic changes in actin organization resulting in the formation of dense actin networks with high turnover rates, a phenotype that is consistent with cells that are rapidly undergoing cytoplasmic reorganization. Together the data suggest that the BBM transcription factor activates a complex network of developmental pathways associated with cell proliferation and growth.